1. Field of the Invention
The present invention pertains to installation and utilization of a remotely operated manipulator system in a confined enclosure, by way of a relatively small port. It includes installation of the system in a radioactive, confined enclosure, and installation of a nozzle dam in a nozzle of the enclosure by the system without need for an operator in the enclosure.
2. Description of the Prior Art
A variety of apparatus and methods are taught for performing work in an enclosure that is confined or that presents an unsafe environment such as in a heat exchanger water box, whereby the operator can conduct the operation from outside the enclosure.
One such environment includes both hazards for an operator. It is within the heat exchanger portion of a nuclear reactor boiler. The present invention will be described with respect to that most demanding application, although it should be understood that application of the present invention includes other areas such as performing work behind any wall having an access port.
A nuclear reactor boiler heats water for steam by transferring heat from radioactive reactor water, through heat exchanger tubes, to nonradioactive water.
The boiler receives the super heated radioactive water from the core of the reactor by way of an inlet port or "inlet nozzle" into a typically five foot high first sealed cavity occupying about one half of the rounded bottom of the boiler. The water is drawn upward through parallel, vertical heat exchanger tubes within the boiler which begin from openings in the roof of the cavity. The tubes extend within the boiler to the top of the boiler and then turn downward to open into the roof of a second sealed cavity which shares a partition with the first cavity at the bottom of the boiler. The water is drawn from the second cavity by way of an outlet port or "outlet nozzle" by means of an external pump. The roof comprising the open ends of the tubes is sometimes called a "tube sheet".
The radioactive first and second cavities and tubes must be emptied of radioactive water for periodic cleaning which may include inspection and repair.
Regarding the first cavity, the input port must be sealed for safety by a nozzle dam such as the SEGMENTED NOZZLE DAM described in U.S. Pat. No. 4,957,215 patented by Evans et al. on Sep. 18, 1990. This holds back the reactor water to permit safe occupation of the first cavity by an operator in protective garb. It also permits cleaning elements of the cavity without having to lower water in the reactor core in order to keep water out of the first cavity.
Regarding the second cavity, the output port must also be sealed because a static water head is above both cavities at certain times. The second cavity must also be accessed for cleaning and servicing.
A limited access, circular, shoulder-wide approximately 16" diameter standardized port called a "manway" is provided in the wall of each cavity 90 degrees around from the applicable inlet or outlet port so that an operator can enter the cavity to install the dam and participate in the cleaning operation. Permissible maximum time for any one operator in the cramped radioactive environment of the boiler cavity is limited to only minutes per year, as determined by the radiation exposures commonly found in such boiler cavities.
When used in this demanding application, the present invention reduces the man minute and therefore man-REM exposure in the radioactive boiler needed for a cleaning or servicing operation. It also eliminates personal safety problems in the slippery, environmentally hot (radioactive) cavity where accidents have been known to have occurred in the past.
U.S. Pat. No. 4,168,782, patented by Sturges, Jr. Sep. 25, 1979 describes a remote access manipulator for limited access areas such for working on a tube sheet within a primary outlet plenum of a nuclear steam generator.
A slave carriage and manipulator arm for accessing the plenum are operated by duplicating in them, the motion of a miniaturized model that is moved by the operator.
The manipulator arm moves in and out of the manway entrance to the plenum by traveling on a track that passes through the manway. The track is attached near one end to the outside of the manway. It passes through the manway, and leans away from the manway within the plenum where it is supported against the plenum inner wall by an adjustable foot.
The arm includes a base that moves on cam rollers which are disposed in the track and moved by a chain.
The carriage includes cam locks which may be inserted in tube holes in the tube sheet, whereby the carriage is able to traverse the tube sheet in an unlimited number of directions by repeated repositioning and locking into the tube sheet while rotating upon one of the cam locks.
During installation, the track is introduced through the manway and bolted into place. The arm is then assembled with a first end of the arm on the portion of the track that extends out of the steam generator. Next, the arm is cranked into the steam generator along the track by means of a chain, with the second end of the arm extending back out through the manway.
The carriage is then attached to the second end of the arm, and taken into the plenum by the arm and positioned against the tube sheet for attaching the carriage to the tube sheet by the cam. The arm is then operated to disconnect from the attached carriage, and reach back through the manway to take tools for installing in a tool operating location in the carriage for work on the tubes.
U.S. Pat. No. 4,179,035, patented Dec. 18, 1979 by Francois et al., describes a master-slave manipulator for performing work in an enclosure such as a water box of a heat exchanger for a pressurized-water reactor.
The master and slave portions of the manipulator are counterbalanced from a connecting shaft and operatively connected by pulleys and chains over rotatable joints. The slave portion of the manipulator is operated by manipulating the master portion by hand.
The manipulator is supported by the connecting shaft which is rotatably mounted through the center of a plate designed for mounting over an opening in the wall of the enclosure. The plate includes trunnions for supporting it during transport.
To install the manipulator in the enclosure for work therein, the manipulator assembly is carried at the trunnions by a jack-operated supporting arm of a dolly that is used to position the plate over the opening. The positioned plate covers the opening, with the slave portion of the manipulator extending into the enclosure.
Holes are provided through the plate for the introduction of inspection equipment such as an endoscope, lamp or television camera, to the interior of the enclosure.
U.S. Pat. No. 4,919,194, patented Apr. 24, 1990 by Gery et al. describes a method for installing a robot arm in an operating zone within a containment vessel that includes an access opening, such as in a steam generator of a pressurized-water nuclear power station.
The robot arm includes at its first end, a compass arrangement consisting of two hinged-together arms with a foot plate at the second end. The foot plate is attached to a carriage or dolly by which the folded robot may be moved into position under the vessel.
Once in position under the vessel, the second end of the robot arm attaches to a first support point having known coordinates with respect to the opening of the vessel such as an attachment bracket mounted on the floor of the room. The foot plate at the first end then detaches from the carriage and moves to a second support point of known coordinates that is adjacent to the opening, where the foot plate is then affixed. The second end of the robot then detaches from the bracket, and is free to receive tools and enter the access opening for working in the operating zone with reference to coordinates of the second support point.
U.S. Pat. No. 4,954,312 patented by McDonald et al. on Sep. 4, 1990, describes a method for remotely installing a dam unit in a nozzle of a nuclear steam generator head, by use of a manipulator arm which has a clamp or jaw member. The method includes passing the manipulator through a manway in the wall of the head and attaching the manipulator by a mounting pedestal to a head internal surface such as the inward facing surface of the wall, or to a plurality of tube ends in the tube sheet that is in the enclosure.
Once the manipulator is secured to the tube sheet, it is fed segments of the dam unit by way of the manway, each segment being dovetailed to fit with the previous segment to build the dam unit. The segments are each fed to the manipulator by sliding a successive one on the last one, and fastening lock bolts. The assembled dam unit is then moved within the head by the manipulator, to the nozzle and positioned there for sealing the nozzle. Hold down bars are then attached to the head to help support the dam against hydraulic load.
U.S. Pat. No. 4,959,192 patented by Trundle et al. on Sep. 25, 1990 describes a system for moving a nozzle dam into the head of a nuclear reactor steam generator, locating it over the nozzle, and bolting it down.
In this system, a rod with appropriate tooling is extended through the manway to attach a pulley to the tube sheet over the nozzle. A rope which runs over the pulley and which has its first end outside the manway is attached by its second end to strapping means which holds the nozzle dam in a folded condition.
With help of the rope, the pulley, and a hook pole, the nozzle dam is taken into the head, unfolded and positioned over the nozzle. It is bolted down by a torquing tool and a torquing machine that is similarly brought in by the rope and pulley, wherein the pulley may be temporarily attached to the tube sheet over the manway if desired.